The present invention relates to a detection device and to a method for producing such a detection device.
Detection devices for detecting a property of a medium are known from the prior art.
Such detection devices typically have a detection sensor, wherein the detection sensor is arranged in a housing of the detection device. Such a housing is typically composed of plastic, wherein it is fabricated by means of an injection molding method. In addition, such a housing has a housing cover, which is typically also fabricated from plastic as a one-piece molded part by means of an injection molding method.
The housing cover is then attached to the housing in an assembly step of the detection device together with a seal, for example an injection-molded-on silicone seal, and the seal protects the detection sensor against disruptive extraneous influences.
In order to position the medium whose properties are to be detected against the detection sensor of the detection device, an inlet opening is typically made in the housing cover. Within the scope of the present invention, the housing cover forms, instead of an inlet opening, an inlet duct with an inlet port, via which the detection device can be connected to the medium. Such an inlet duct with an inlet port is interesting when, for example, properties of a medium in a volume, such as for example in a hose, which is for example fabricated from silicone and is configured to detect impacts of pedestrians on a vehicle are to be detected.
In order to avoid falsifying the detection of the properties of the medium, a compensation element is arranged on the detection device, typically on the housing cover. The compensation element is configured in such a way that it has a defined compensation rate. The compensation rate must be selected such that changes in the properties of the medium are detected in a range which is relevant for the subsequent applications, but other changes are compensated. This typically means during the detection of impacts that rapid increases in pressure owing to impacts must continue to be detectable, while slow changes in pressure owing to changes in temperature or altitude have to be compensated. For this purpose, the compensation element is mounted on or at an opening in the detection device, for example on the housing cover, which opening comes to be significantly smaller than the inlet opening which is provided, or in the present case smaller than the opening which the inlet duct with the inlet port has.
Hitherto, the compensation opening which is necessary for the compensation could either be formed with a correspondingly configured shaping tool, in a step with the formation of the inlet duct, or with a separate shaping tool in an opposite way to the shaping tool. In this context, for example for the inlet duct a duct diameter of 4 mm was selected, and for the compensation opening an opening diameter of 0.8 mm. A compensation element, for example a pressure compensation element which can be bonded in, could be bonded onto the compensation element in a further method step. By configuring the inlet duct in such a way that a first section of the inlet duct and a second section of the inlet duct are arranged at an angle different from zero to each other, it is no longer possible to demold the inlet duct with the previous fabrication method. A bonded-in pressure compensation element with a relatively large diameter in order to implement the demolding is, however, not expedient, since the air throughput rate would become too large and the pressure signal would be falsified.